Electric circuit breaker



May 15, 1934. l H. TRENCHAM' 1,959,224

ELECTRIC CIRCUIT BREAKER Filed Sept. 14, 1932 4 3 I B Z Y Inventor: Hen-m Trenchobm, y I His Attorney Patented May 193.4

UNITED STATES ELECTRIC CIRCUIT BREAKER Henry Trancham, Ruislip, England, assignor to General Electric Company, a corporation of New York Application September 14,1932, Serial No. 633,193

In Great Britain October 15, 1931 2 Claims. (Cl. 200-350) The present invention relates to electric circult breakers of the oil-break type in which an arc formed between two contacts in the breaker is extinguished by a blast of arc extinguishing fluid, as oil, forced between the contacts durin their separation.

Various arrangements have been proposed for producing the necessary blast of oil for extinguishing an are by means of a second are drawn between contacts which are in series with those between which the arc to be extinguished is produced, the second, or pressure generating arc, being arranged to be drawn concurrently with or prior to the are which is to be extinguished forth in the following description referring to the accompanying drawing, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, the single figure thereof is an elevational View, partly in section, of an electric circuit breaker embodying the present invention.

In accordance with'one method of practising the present invention there is interposed between a stationary hollow contact, as a tubular conductor, and a second contact movable with relation to the stationary contact a third or floating contact having contact surfaces cooperating both with the hollow stationary contact and the mov-,

able contact, the third contact having a lost motion connection with the movable contact under the control of resilient means. The arrangement is such that, as the movable contact is separated from the stationary contact, the cooperating-contact surfaces of the hollow [or tubular contact and the third contact are maintained in engagement under the bias of the resilient means until the whole of the lost motion has been taken up, whereupon the stationary and third contacts separate. The are produced between the stationary and "third contacts is then extinguished by the blast of oil produced by the pressure developed by the are previously formed between the movable contact and the third contact. I

The circuit breaker illustrated comprises a.

pair of tubular stationary conductor studs1 and 2 forming the lead-in conductors. A conducting bridging member or crossbar 3 carried by a suitable operating rod 4 and operatively connected with the actuating mechanism (not shown) of the circuit breaker is arranged to interconnect the conductor studs in the closed circuit position. The operating rod .4 is insulated from the crossbar 3 in a ner by the insulator 5.

The stationary contactportions comprise the arcing contact members 6, each being annular in form and suitably secured, as by threaded engagement, to the lower end of the corresponda ing conductor stud. The tubular conductor studs are supported from the base of the cover chamber 8 of the circuit breaker and are insulated therefrom by the insulating tubes 9. Removable terminal members 10 which can be screwed into the upper ends'of the studs 1 and 2, are supported within insulating bushings 11 extending through the upper cover of the chamber 8.

The movable contacts 12 cooperating with the stationary arcing contacts 6 are carried at opposite ends 01' the crossbar 3, and interposed between the aforesaid movable and stationary contacts are intermediate third or floating contacts 13. These third contacts are. carried by an insulating member 14 in turn supported by the crossbar 8 and movable with it. The contacts 13 are therefore insulated from the contacts 12 except when 'said contacts are in engagement with each other.

The insulating member 14 has a limited degree of lost motion, with respect to the crossbar ,3 under the controloi resilient means shown as springs 17. These springs are arranged to surround guide pins 18 which connect the member 14 with the crossbar 3 .for normally separating the contacts 12 and 13. The pins 18 determine able insulating or are extinguishing fluid contained within the main tank 15.

In the fully closed position of the switch, the arcing contact portions 6, the intermediate floating contacts 13 and the contacts 12 at each end of the crossbar 3 are in engagement with one another and the circuit is therefore completed between the stationary contacts through the crossbar 3-. The contact surface of the third contact which coacts with the hollow stationary contact is arranged to enter into or abut the holsuitable manlow contact so that the hollow contact is substantially closed or sealed when the switch is in the closed circuit position. The hollow contact is suitably supported upon the cover of a tank containing oil within which the contacts are im-- mersed, and is provided with suitable apertures for guiding the oil blast as hereinafter described.

Preferably the cover of the breaker is constructed to provide a chamber separate from the main breaker tank into which the oil can be exhausted, the hollow cover also being provided with small apertures through which the oil exhausted thereinto can return to the braker tank. The breaker tank is then completely enclosed and separated from the hollow cover so that the pressure developed in the tank by the pressure are is effective in driving oil through the hollow contact and extinguishing the arc drawn therefrom.

On the initial opening of the switch, the crossbar 3 moves downwards, but the springs 17 maintain the intermediate contacts 13 in engagement with the arcing portions or tips 6 until the whole of the lost motion permitted by the pins 18 has been taken up. During this movement a pressure generating arc is drawn between each of the movable contacts 12 and the intermediate contacts 13. These arcs vaporize the oil or insulating liquid in which the contacts are immersed and cause a considerable increase in pressure in the tank 15. When the whole of the lost motion has been taken up, the arcing tips 6 and the contacts 13 separate and the oil is forced into the tubular studs and the arc extinguished by the resulting oil blast. In the drawing the circuit breaker is shown shortly after separation of the arcing tips 6 and contacts 13.

By way of example, the maximum separation between the intermediate contacts 13 and the movable contacts 12 may be of the order of A, in order to limit the length of the are produced and the consequent vaporization and presof pressure within the tank forming the pressure chamber, an air space may be left above the level of the oil in the tank 15 to act as a cushion.

It should be understood that the present invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of the invention.

What I claim as new and desire to secure by Letters Patentin the United States is:

1. An electric circuit breaker having a pressure chamber containing insulating oil, stationary contact structure comprising a pair of tubular con ductor studs mounted in and extending through a wall of said chamber, each of said studs having a passage exhausting exteriorly of said chambet and provided with a contact portion at the end of the passage within said chamber, and movable bridging contact structure disposed within said chamber interconnecting said conductor studs including a pair of movable contacts carried by a conducting bridging member, and a pair of intermediate floating contacts, said floating contacts carried by insulating structure and having a limited degree of lost motion with respect to said bridging member so that circuit opening movement of said bridging structure produces a pair of initial pressure generating arcs between said movable and floating contacts forcing oil into said tubular studs to exhaust exteriorly of said chamber.

2. An electric circuit breaker comprising a tank forming a pressure chamber containing oil, a cover structure for said tank forming an oil collecting chamber above said pressure chamber, a pair of stationary tubular conductor studs extending through a wall of said pressure chamber, each of said studs having a passage exhausting from said pressure chamber into said upper chamber, movable contact structure disposed in said pressure chamber and immersed in said oil coacting with the lower open end of each of said studs comprising a floating contact normally positioned at the opening of the. corresponding stud and a movable contact for engaging said floating contact, said contacts arranged so that a pressure generating arc is formed between said floating and movable contacts for driving oil into said stud and across the are formed at the opening thereof.

HENRY 'IRENCHAM. 

